Wide angle attachment



.M 0 R H Pu DH A E S R0 S1 2 Q 2 5 1 3 R 0 x wwc/ v 1964 D. E. GUSTAFSON 3,152,210 T2033 WIDE ANGLE ATTACHMENT Filed May 1. 1961 In JIZIOV'.

United States. Patent O 3,152,210 WIDE ANGLE ATTACHMENT Darryl E. Gustafson, Glenview, lll., assignor to Bell & Howell Company, Chicago, [1]., a corporation of Illinois Filed May 1, 1961, Ser. No. 106,692 1 Claim. (Cl. 88-57) This invention relates to a wide angle attachment for a zoom lens, and more particularly to a wide angle attachment for use with a zoom lens and corrected over the entire range of acl'ustment of the zoom lens. W #A fl ob ect of the invention is to provide an afoczfi wide angle attachment for a zoom lens to increase th magnification range of the zoom lens Ano'ther object of the inventio'ri is to provide a wide angle attachment for use with a zoom lens having a stop and highly corrected for the apparent shifting of the stop when the zoom lens is adjusted.

Another object of the invention is to provide a wide angle attachment having a front negative group including a negative meniscus front component and a negative second component along with a rear positive component.

It is to be understood that the terms front and rear as herein used refer to the left and right ends of the attachments respectively and to the ends of the objectives respectively nearer the longer and shorter conjugates thereof.

A complete understanding of the invention may be obtained from the following detailed description of wide angle attachments and zoom objectives forming specific embodiments thereof, when read in conjunction with the appended drawings; in which the single figure is a longitudinal section of a wide angle attachment and a zoom lens which together form one embodiment thereof.

The invention provides an afocal wide angle attachment for a zoom lens in which the attachments are corrected over ranges of adjustment of the zoom lenses. Each of the attachments includes a negative front lens group and a positive rear group or member. The front lens group comprises an achromatized negative meniscus front component and a biconcave lens positioned therebehind. The rear group or member comprises a plurality of positive singlets. The attachment is highly corrected for use with a zoom lens in which the apparent positions of the stop therein shifts during zooming.

Referring now in detail to the drawings, there is shown in the figure a highly corrected afocal wide angle attachment 10 adapted for use with a zoom lens 11 when the lens is in any of its zooming positions. The attachment 10 comprises a negative front lens group or member 1 and a positive rear member 2. The front group has an achromatic, negative meniscus front component consisting of lenses L and L and closely spaced biconcave second and rear singlet components L the front component being concave to the rear. The positive member 2 consists of two closely spaced biconvex singlets L and L spaced substantially from the front lens group. The lenses L to L have spherical optical surfaces or radii of curvature R to R axial thicknesses 1 to 1' and axial separations s to s The attachments 10 is designed to be mounted in front of a zoom lens or objective 11 with an axial separation .9 and the zoom objective 11 includes a front lens group 3 adjustable for focusing and movable non-linearly for focus compensation during zooming, a linearly movable lens group 4, a positive rear lens group 5, and a stop or diaphragm (not shown) being positioned between the member 4 and lens group 5. The zoom lens 11 includes lenses L to L having spherical optical surfaces of radii of curvature R to R axial thickness t, to t and axial separations s to s During zooming the lens 3,152,210 Patented Oct. 6, 1964 group 5 and stop are fixed relative to the focal plane which is positioned to the rear of the lens group 5, the the group 4 is moved linearly in one direction and the lens member 3 is moved non-linearly. The zoom lens 11 is shown in its extreme telephoto adjustment, for which position the attachment substantially increases the field covered, the attachment having a negative magnification of about 1.4.

A preferred embodiment of the attachment 10 is constructed in conformity with the following table in which dimensions are in terms of inches, and the indices of refraction for the sodium D line and the Abbe dispersion numbers are respectively designated at n and V:

R =+2.857 L1 i =.30O n =l.720 V=29.3

Ra=-3.636 L: tz=.l00 'na=1.523 V=58.6

81=.350 R4=1.429 L3 i3=.100 nd=1.689 V=30.9

s2=.300 Rfl=+3.704 L t4=.225 na=l.620 V=60.3

83=.005 R5=+25.000 Ls t =.200 nd=1.620 V=60.3

For high correction, the attachment 10 should be constructed in substantial compliance with the following inequalities:

Power of doublet Lr-Lz Power of member 1 Power of surface R 0 Power of member 2 A preferred form of the zoom lens 11 is constructed in conformity with the following table in which dimensions are in terms of inches, and the indices of refraction for the sodium D line and the Abbe dispersion numbers are respectively designated at In, and V:

[Equivalent focal length .254 Wide angle, .3556 Mean, .508 Telephoto.

Back focal length .382. Apcrturej/LS] 3 4 While the invention is thus described, it is not wished to be limited to the precise details described, as changes R1=+2.857 may be readily made without departing from the spirit 33:43.636 of the invention. n R 971 iz=-1 0 na=1.523 V=58.6

What is claimed is: 5 v a- .1=.350 In a wide angle attachment, proceeding from front to L1 R*= 1-429 83:10,) "F1639 V=30 9 rear, a negative meniscus cemented doublet front com- Rs=+3.846 ponent, a biconcave singlet second component, a bicon- R6=+3J04 F300 vex singlet third component, and a biconvex singlet fourth L4 10 R1--2.222 component and being further characterized in that the 8a=.005 attachment conforms substantially to the following table L5 $200 d=1 620 7:603 in which dimensions are in terms of inches, and proceeding from front to rear L to L designate the lenses, R to R the radii of curvature of the surfaces, t to t the 15 References Clted 111 the file of this Patent axial thicknesses, s s, and .9 the axial separations, n UNITED STATES PATENTS the indices of refraction for the sodium D line and V 2,789,463 Kohler et aL APR 23, 1957 the Abbe dispersion numbers: 2,944,464 Rosin July 12, 1960 

